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Chun Liu

Publications and source records attributed to Chun Liu.

45 records · Page 3Linked to original sources
PubMed2003

Exposing ferrets to cigarette smoke and a pharmacological dose of beta-carotene supplementation enhance in vitro retinoic acid catabolism in lungs via induction of cytochrome P450 enzymes.

In our previous studies, we found lower levels of retinoic acid (RA) in the lungs of ferrets exposed to cigarette smoke and/or a pharmacological dose of beta-carotene. To determine whether this is involved in excessive catabolism of RA via cytochrome P450 (CYP) induction, we carried out in vitro incubations of RA with the lung microsomal fractions of ferrets with or without CYP inhibitors and antibodies against CYP. The polar metabolites (4-oxo-RA and 18-hydroxy-RA) of RA metabolism after the incubation were analyzed by HPLC. Expressions of CYP (1A1, 1A2, 2E1 and 3A1) were examined using Western blot analysis. Incubation of various concentrations of RA with the lung microsomal fraction from ferrets exposed to cigarette smoke, a pharmacological dose of beta-carotene or their combination dose-dependently increased the levels of 4-oxo-RA and 18-hydroxy-RA compared with that of the control ferrets. At all RA concentrations, this increase was the greatest in lung tissue from the combined treatment group. Furthermore, this enhanced RA catabolism was substantially (approximately 80%) inhibited by nonspecific CYP inhibitors (disulfiram and liarozole), but was partially (approximately 50%) inhibited by resveratrol (CYP1A1 inhibitor), alpha-naphthoflavone (CYP1A2 inhibitor) and antibodies against CYP1A1 and CYP1A2. Cigarette smoke exposure and/or pharmacological doses of beta-carotene increased levels of CYP1A1 and 1A2 by three- to sixfold but not levels of 2E1 and 3A1 in ferret lung tissue. These findings suggest that low levels of RA in the lung of ferrets exposed to cigarette smoke and/or pharmacological doses of beta-carotene may be caused by the enhanced RA catabolism via induction of CYP, CYP1A1 and CYP1A2 in particular, which provides a possible explanation for enhanced lung carcinogenesis seen with pharmacological doses of beta-carotene supplementation in cigarette smokers.

Analysis of Variance↗
PubMed2003

Effectiveness of intermittent -Gx gravitation in preventing deconditioning due to simulated microgravity.

This study was designed to compare the effectiveness of daily short-duration -Gx gravity exposure in preventing adverse changes in skeletal and cardiac muscles and bone due to simulated microgravity. Tail suspension for 28 days was used to simulate microgravity-induced deconditioning effects. Daily standing (STD) at 1 G for 1, 2, or 4 h/day or centrifugation (CEN) at 1.5 or 2.6 G for 1 h/day was used to provide -Gx gravitation as a countermeasure. The results indicate that the minimum gravity exposure requirements vary greatly in different systems. Cardiac muscle is most responsive to such treatment: 1 h/day of -Gx gravitation by STD was sufficient to prevent adverse changes in myocardial contractility; bone is most resistant: 4 h/day of -Gx gravitation only partially alleviated the adverse changes in physical and mechanical properties of the femur. The responsiveness of skeletal muscle is moderate: 4 h/day of -Gx gravitation prevented mass reduction and histomorphometric changes in the soleus muscle during a 28-day simulation period. Increasing gravitational intensity to 2.6 G showed less benefit or no additional benefit in preventing adverse changes in muscle and bone. The present work suggests that system specificity in responsiveness to intermittent gravity exposure should be considered one of the prerequisites in proposing intermittent artificial gravity as a potential countermeasure.

Adrenal Glands↗
PubMed2003

[Evaluation oxygen free radicals related index before liver transplantation to forejudge prognosis].

OBJECTIVE: To research the relationship of oxygen free radicals related index before liver transplantation with prognosis. METHODS: Lipid peroxide (LPO), total antioxidant capacity (TAC), nitric oxide (NO) and total bilirubin (T-BIL) in blood from 18 patients were measured before liver transplantation, and the relationship with prognosis was analyzed. RESULTS: The blood LPO of death group was (17.13+/-4.16) micromol/L, it was obviously higher than that of survival group (7.97+/-3.52) micromol/L (P<0.05). The blood TAC of survival group was (38.05+/-19.13) kU/L, it was higher than that of death group (32.54+/-3.07) kU/L, but there was no obvious difference(P>0.05). There was no obvious difference between the blood NO of death group was (50.80+/-14.80) micromol/L, and survive group was (150.46+/-19.54) micromol/L (P>0.05). The blood T-BIL of death group was (425.98+/-214.18) micromol/L, it was obviously higher than that of survival group (172.10+/-144.32) micromol/L (P<0.05). So the blood LPO and TAC were chosen as the index to forejudge prognosis, and an equation was established to forecast if the patient would be death or survive: Y(1)=0.329 0 X(1)+0.099 8 X(2)-3.9040, Y(2)=1.352 0 X(1)-0.0500 X(2)-11.4640, X(1) represented serum LPO, X(2) represented serum TAC. 100.0 percent accuracy was forecasted in the survival group by the equation, 83.3 percent accuracy was in the death group. The overall patients were forejudged 94.4 percent accurately. CONCLUSION: Measuring LPO and TAC in blood maybe forejudging prognosis properly and can be used as routine examination before liver transplantation. The equation is preferable to forejudging prognosis, it can be used to choose from high risk patients to improve survival rate of the patients after operation. Therefore, it is valuable in clinical practise.

Adult↗
PubMed2003

Daily 4-h head-up tilt is effective in preventing muscle but not bone atrophy due to simulated microgravity.

To assess the potential value of intermittent artificial gravity as an efficient countermeasure, our previous studies have showed that daily 4-h standing (STD) is sufficient in counteracting muscle atrophy but not bone atrophy induced by simulated microgravity. The aim of the present study was to determine whether intermittent gravitational loading by daily 2-h or 4-h, +45 degrees head-up tilt (HUT) is more effective than STD in counteracting muscle and, particularly, bone atrophy due to simulated microgravity. Sprague-Dawley male rats weighing 290-300 g were subjected to a 28-d tail-suspension to simulate microgravity deconditioning. Daily HUT for 2, or 4 h was used to provide intermittent gravitational loading in foot-ward and tail-ward directions. The results showed that 4 h/d HUT was sufficient, and 2 h/d was less effective, in preventing adverse changes in muscle weights, fiber types, and cross-sectional areas (CSA) of muscles due to a 28-d simulated microgravity. The % protections by 4 h/d HUT in maintaining the CSAs of type I fibers in soleus, medial and lateral gastrocnemius and extensor digitorum longus muscles were 103%, 82%, 102%, and 83%, respectively. However, according to changes in physical and mechanical properties of femur, daily 4-h HUT was ineffective in attenuating the adverse changes in bone due to a 28-d simulated microgravity. Reductions in wet, dry, and ash weights and decreases in mechanical strength of femur did not show significant improvement by daily 2-h or 4-h HUT. Taken together, the findings indicate that the countermeasure effectiveness of daily 2-h or 4-h HUT for muscles is comparable with that by daily STD with the same durations. Daily 4-h HUT, as 4-h STD, is also ineffective in attenuating adverse changes in bone mass, but seems partially effective in preventing declines in mechanical properties due to simulated microgravity.

Animals↗
PubMed2002

Exclusive and complete introduction of amino groups and their N-sulfo and N-carboxymethyl groups into the 6-position of cellulose without the use of protecting groups.

A new regioselective synthesis of 6-amino-6-deoxycellulose with a DS 1.0 (degree of substitution) at C-6, and its 6-N-sulfonated and its 6-N-carboxymethylated derivatives, without using protecting groups is described in this paper. The reaction conditions were optimized for preparing cellulose tosylate with full tosylation at C-6 and partial tosylation at C-2 and C-3. The nucleophilic substitution (S(N)) reaction of the tosyl group by NaN(3) at low temperature of 50 degrees C in Me(2)SO was achieved completely at C-6, whereas the tosyl groups at C-2 and C-3 were not displaced. In contrast to this, at 100 degrees C the tosyl groups at C-6, and also those at C-2 and C-3, were replaced by azido groups. This regioselective reaction that depends on temperature makes it possible to reach a selective and quantitative S(N) reaction at C-6 at low temperatures. In the subsequent reduction step with LiAlH(4), the azido group at C-6 was reduced to the amino group, and the tosyl groups at C-2 and C-3 were simultaneously completely removed. Also reported is a temperature-dependent, regioselective and complete iodination by nucleophilic substitution of the tosyl group at C-6 at 60 degrees C. At higher temperatures from 75 to 130 degrees C, substitution is also observed to occur at C-2. The selective iodination at 60 degrees C was employed to confirm the complete tosylation at C-6 of cellulose. The reaction products were identified by four different independent quantitative methods, namely 13C NMR, elemental analysis, ESCA, and fluorescence spectroscopy. 6-N-Sulfonated and 6-N-carboxymethylated cellulose derivatives were also synthesized. The new derivatives are potent candidates for structure-function studies, e.g., studies in relation to regioselectively 2-N-sulfonated and 2-N-carboxymethylated chitosan derivatives.

Amines↗
PubMed2002

Kinetic theory for flows of nonhomogeneous rodlike liquid crystalline polymers with a nonlocal intermolecular potential.

The Doi kinetic theory for flows of homogeneous, rodlike liquid crystalline polymers (LCPs) is extended to model flows of nonhomogeneous, rodlike LCPs through a nonlocal (long-range) intermolecular potential. The theory features (i) a nonlocal, anisotropic, effective intermolecular potential in an integral form that is consistent with the chemical potential, (ii) short-range elasticity as well as long-range isotropic and anisotropic elasticity, (iii) a closed-form stress expression accounting for the nonlocal molecular interaction, and (iv) an extra elastic body force exclusively associated with the integral form of the intermolecular potential. With the effective intermolecular potential, the theory is proven to be well posed in that it warrants a positive entropy production and thereby the second law of thermodynamics. Approximate theories are obtained by gradient expansions of the number density function in the free energy density.

Journal Article↗
PubMed2002

Chlormethiazole treatment prevents reduced hepatic vitamin A levels in ethanol-fed rats.

BACKGROUND: Chronic ethanol intake results in decreased hepatic vitamin A levels through both enhanced degradation of vitamin A via a cytochrome P450 enzyme (CYP)-dependent process and increased mobilization of vitamin A from the liver into the circulation. This study investigated whether treatment with chlormethiazole, a CYP inhibitor, restores vitamin A in the livers of ethanol-fed rats. METHODS: Ethanol-exposed and non-ethanol-exposed rats were treated with or without chlormethiazole (10 and 100 mg/kg body weight) for 1 month. Liver and plasma levels of retinol and retinyl palmitate were analyzed by high-performance liquid chromatography. Expressions of hepatic lecithin:retinol acyltransferase (LRAT) and cellular retinol-binding protein were analyzed with reverse transcription-polymerase chain reaction. Hepatic retinol esterification by LRAT was examined by using incubations of the microsomal fractions of livers with exogenous sources of retinol. RESULTS: Ethanol-feeding in rats for a month resulted in lower hepatic levels of retinol and retinyl palmitate than those found in controls and the occurrence of several polar retinoid metabolites. In contrast, treatment with chlormethiazole at two different doses in ethanol-fed rats completely blocked the formation of hepatic retinoid polar metabolites and restored hepatic levels of retinol and hepatic retinyl palmitate in a dose-dependent manner. Furthermore, increased plasma concentrations of retinyl palmitate in rats fed with ethanol, which indicate increased mobilization of vitamin A, were partially inhibited by chlormethiazole treatment. However, neither ethanol nor chlormethiazole treatment altered the expression and activity of LRAT in the liver of rats. Hepatic expression of cellular retinol-binding protein increased significantly in ethanol-fed rats with or without chlormethiazole treatment compared with control rats. CONCLUSIONS: These data suggest that chlormethiazole can restore both hepatic retinol and retinyl ester concentrations to normal levels in ethanol-fed rats through blocking enhanced both degradation of vitamin A and mobilization of vitamin A from the liver into the circulation.

Alcohol Drinking↗
PubMed2002

Emphysematous lung destruction by cigarette smoke. The effects of latent adenoviral infection on the lung inflammatory response.

This study was designed to test the hypothesis that cigarette smoke-induced inflammation and emphysema are amplified by the presence of latent adenoviral (Ad) infection, and to determine whether this emphysematous process can be reversed by all-trans-retinoic acid (RA) treatment. The results confirm that in guinea pigs, chronic cigarette-smoke exposure caused lesions similar to human centrilobular emphysema. They also show that latent Ad infection combined with cigarette-smoke exposure caused an excess increase in lung volume (P < 0.001), air-space volume (P < 0.001), and lung weight (P < 0.01), and further decrease in surface-to-volume ratio (P < 0.001) compared with smoke exposure alone. RA treatment failed to reverse these emphysematous changes. Analysis of inflammatory response in parenchymal and airway tissue showed that smoking caused an increase of polymorphonuclear leukocytes (PMNs) (P < 0.0002), macrophages (P < 0.001), and CD4 cells (P < 0.0009), and that latent Ad infection independently increased PMNs (P < 0.001), macrophages (P = 0.003), and CD8 cells (P < 0.001). We conclude that latent Ad infection amplifies the emphysematous lung destruction and increases the inflammatory response produced by cigarette-smoke exposure. In this study, the increase in CD4 was associated with cigarette smoke and the increase in CD8 cells with latent Ad infection.

Adenoviridae↗